Large numbers of older oil wells in the U.S. bypassed relatively thin oil-bearing formations, whose recovery was not economical at the time those wells were drilled. Production of oil from formations that were thus bypassed represents a significant opportunity in an era of higher oil prices. Many of these previously bypassed zones are now being reworked. Oil production from thin zones and depleted older producing zones is commonly accompanied by substantial water production. Hydraulic fracturing is the principal technique for stimulating production from thin zones and depleted fields. This technique typically results in a pair of vertical wing fractures extending into the formation. In thin zones or depleted formations, the fractures commonly intersect water-bearing formations, resulting in the recovery of oil cut with water. The cost of separating the oil from the recovered oil and water mixture, and disposing of the water, is significant.
Jet drilling rotors are capable of drilling porous rock such as sandstone, with low thrust and zero mechanical torque. These tools can be made very compact, enabling the tools to conform to a small bend radius. Ultra-short radius jet drilling offers the potential to drill production holes entirely within the oil- or gas-bearing volume of a producing formation, or within a previously bypassed formation, such as those noted above. This approach should minimize the amount of water recovered with the oil, while simultaneously enabling the recovery of oil from a relatively large area.
Lateral completion wells in thin producing zones with good vertical permeability provide the greatest potential for increased production relative to vertical wells. The target formations for lateral drilling are typically relatively thin (i.e., ranging from about 2 to about 10 meters in thickness) formations that were bypassed in existing production wells. Jet drilling tools provide effective drilling at minimal thrust in permeable oil and gas producing formations, but may not effectively drill through impermeable cap-rock. The objective when drilling such formations is to drill a curved well within the formation thickness, implying the need to drill around a short radius curve having a minimum radius of about 1 meter (40 inches). Working within such a tight radius cannot be achieved using small diameter steel or titanium coiled tubing without exceeding the elastic yield of the tubing and generating a set bend that prevents subsequent straight hole drilling. Composite tubing capable of elastic bending through a small bend radius is available (for example, from Hydril Advanced Composites Group of Houston, Tex.). Unfortunately, such composite tubing generally exhibits maximum pressure ratings of about 35 MPa (˜5000 psi), which is too low for many jet drilling objectives. Wire-wound high-pressure hose capable of bending though a short radius is also available (for example, from the Parflex Division of the Parker Hannifin Corporation in Ravenna, Ohio). Unfortunately, such wire-wound high-pressure hose is very flexible, and will buckle if employed to drill lateral completion wells. It would therefore be desirable to provide a hose assembly configured to deliver high-pressure jetting fluid to a jet drilling tool, where the hose assembly is sufficiently flexible to pass through a short radius curve without damage or acquiring a permanent set, yet is stiff enough to drill a long lateral extension without buckling or locking up in the hole.